A field planted with two kinds of cotton (Gossypium sp): Bt cotton and normal cotton, where the normal cotton acts as a refuge for insects.

Some rows of the field in the photograph contain cotton plants (Gossypium sp) that are genetically engineered to produce a toxin from the bacterium Bacillus thuringiensis (Bt). Bt kills insects that feed on the cotton. Other rows contain cotton plants that are not genetically engineered, and they serve as refuges for the insects. Such refuges are important because they slow the rate at which insects evolve resistance to the genetically engineered cotton. This photograph originally appeared on the cover of Ecological Applications (14:6) in December of 2004.